The attaching of a saddle to a bicycle frame is done using a saddle post that holds means for attaching the saddle to one of its ends, whereas its opposite end is suitable for working with a supporting device by being inserted into a tubular fitting of the latter.
This fitting can consist directly of the top end of a saddle tube of the bicycle frame or a tubular element that is arranged in the saddle tube, in the intersection of the latter and the upper tube of the bicycle frame. The fitting has an inside dimension that is adapted to the outside dimension of the post so as to make it possible for the post to slide inside the fitting in the vertical direction to allow the vertical adjustment of the saddle relative to the crankset shaft for adaptation to the size of the bicyclist.
The supporting device comprises means for locking the saddle post in rotation, as well as means for holding the saddle post in a longitudinal position that is determined relative to the tubular fitting to adjust the height of the saddle. In general, a single tightening device acts as means for locking in rotation, as well as means for holding the saddle post by securing the latter after a certain length of it, which in general should not be less than about 60 mm, is inserted into the fitting.
To achieve the tightening of the saddle post inside the fitting, the latter, at its upper end, generally is slotted, and the tightening device can quite simply consist of a bolt that extends crosswise to bring together the two opposite edges of the fitting until sufficient tightening is exerted on the saddle post relative to the weight of the bicyclist, under all conditions of use.
According to a very common variant, the tightening device comprises a separate tightening collar that is arranged at the top end of the slotted fitting.